Conservative Management of Unicystic Ameloblastoma of Mandible Evolving from Dentigerous Cyst in a Paediatric Patient: A Case Report

Massive cystic lesions involving a mandible always present a diagnostic and treatment challenge. Unicystic ameloblastoma (UA) is a variant of ameloblastoma encompassing about 6% of ameloblastomas. They represent cystic lesions that reveal clinical and radiographic features of a cyst, but the histopathological features demonstrate a typical ameloblastomatous epithelium lining the cyst. It is a variant of ameloblastoma, usually having clinical and radiographic similarities with dentigerous cysts, hence posing preoperative diagnostic difficulties. Adult treatment protocol cannot be applied to the pediatric population since resection may cause an alteration in craniofacial development leading to functional and esthetical damage, which can directly affect their quality of life. A more conservative approach of enucleating the lesion seems to be a promising treatment modality of UA in the pediatric age group. We present a case of mural variant of UA arising from dentigerous cyst in an 8-year-old male patient.


Introduction
Ameloblastoma is the most common locally aggressive benign tumor affecting the mandible. It has many histological subtypes out of which unicystic ameloblastoma (UA) is comparatively less encountered variant possessing slow growth but locally destructive potential [1][2]. UA refers to those cystic lesions, which show clinicoradiographic facade of odontogenic cysts and tumors, but histologically present a typical ameloblastomatous lining epithelium with/without luminal and or mural proliferations thus challenging the surgeons in terms of diagnosis and treatment especially in young children.
Incisional biopsy specimens may not always be representative of the true nature of UA, which may have a negative bearing on the treatment plan [3]. Usually, UA respond well to conservative management, so aggressive protocols like segmental resection should be avoided in children [4]. Here we report a case of mural UA arising from dentigerous cyst lining in an eight-year-old male patient, which was managed through conservative enucleation.

Case Presentation
An 8-year-old male patient, reported to our institute with   (Figure 7).

Discussion
UA is a variant of ameloblastoma, first described by Robinson and Martinez [1] considering the macro-and microscopic appearance, the lesion being essentially a well-defined, large monocystic cavity having a lining, focally composed of odontogenic ameloblastomatous epithelium. They may be associated with an unerupted tooth (dentigerous variant) or lack such association    [1]. Their evolution from epithelial remnants of developing tooth, dentigerous cyst lining or from cystic degeneration of a solid ameloblas toma has long been debated. However, Ackermann et al. [2,5] and Robinson and Martinez [2,5] favored their origin from dentigerous cyst lining owing to common lineage through reduced enamel epithelium and its high neoplastic transformation probability secondary to irri-tants like extraction, trauma, and infections [2,5]. This pathophysiology corresponds with the current case.
Radiographically, UAs have two patterns including unilocular and multilocular, former being commonly associated with dentigerous variant of UAs [2]. The treatment of UAs is still being considered very controversial due to the incongruous use of the term "mural proliferation" [6], which is erroneously interpreted as increased recurrence rate, hence favoring radical resection [1,7]. In fact, the term "mural" describes the extent of ameloblastomatous epithelium penetrating connective tissue wall of a cyst and not that mural ameloblastoma has penetrated the epithelial lining of a cyst [6,8]. Mural UA is believed to recur following enucleation due to remnants of tumor cells in fibrous capsule [9]. Ameloblastoma developing in and limited to the cystic lining and ameloblastoma having micro invasions into the connective tissue wall of the cyst should be managed by enucleation whereas ameloblastoma with complete invasion of the connective tissue thickness should be treated with resection [6,10]. In the current case, conservative enucleation was treatment of choice with satisfactory and uneventful follow up of three years.

Conclusion
This case report highlights the role of histopathologic examination and serial section study from multiple sites of representative specimen as the most sensitive tool for precise diagnosis of UAs and also advocates the conservative treatment approach as the choice of treatment in young children combined with close long term follow up with satisfactory results.